Aleph5....it works!!!

[Jean]

Wow that is huge! It must be really heavy

 

[roddyama]

Hi William,

Are those transformers the special low noise audio transformers from Plitron? If not, where did you get the covers? Do you have covers on the PSU caps or are they just black caps?

Sorry for all the questions.
Rodd Yamashita

 

[wuffwaff]

Jean,

it weighs 30kg.

Rodd,

the transformers are from Schuro here in Germany and are vacuum filled with some kind of raisin (very quiet) and made especially for audio. They now got a new type wich is also magnetically shielded.

The 4 black caps are Albs 40.000/80V wich were left over from another project. (I know 80V is a bit overdone but the space was there)

The chokes are 1.8mH/0.38Ohm

The second batch of caps are 22mFx6 per channel.

william

 

[lifefordota]

Conclusion is that in order to have Aleph 5 drive 4 ohm 60 way, 8 ohm 90 watt , the bias and AC gain have to increase?

 

[wuffwaff]

Hi,

the bias or the ac current gain or both. There are probably a few combinations that will work. I once posted an excel sheet where you can calculate power for different combinations. I think it was called AXE-2.xls

william

 

[lifefordota]

The original aleph 5 , is misleading where 90 watt in 4ohm is not possible?

I'm totally new in diy.
Was planning to make an aleph5

 

[wuffwaff]

It is a long time ago but I think the 90 watts were not possible with 50% ac-current-gain but with 66%.
Play a bit with the excel sheet to find what bias and ac-c-g you need and get an understanding how both work.

william

 

[chede]

Here is wuffwaff's Excel sheet again ...

Thanks again for that, William, I have used it extensively myself in the design of my own Aleph Mini / Aleph-J Single a few years back !


Regards, Claas

 

[lifefordota]

Hi all,

just a pic of the (almost) finished Aleph5. Don´t know how I will finish the case so for now I settle for this "unfinished" look.

Since the last reports I changed the trimmers for R19 and R21 with resistors (49k and 390R) so now it runs at 2.4A bias and about 63% ac current gain (about 6.7A peak).

I will leave it this way and start on a pair of monos with about 31volt rails and 4A bias with 6 paralleled fets. I think this will cure the power problem into 2-3 ohms and make for some happy listening....

william

just change the R19 and R21 from the original scheme will work exactly like what u said? 2.4 A bias and 63 % ac.

also have you compare 2 trafo or single trafo for aleph 5? any benefit?

 

[wuffwaff]

Hi,

it will depend a bit on the exact values of your transistors but approximately yes.

I didn't compare one or two transformers sound wise, the advantage of two was packaging and maybe a bit less mechanical noise.

William

 

[lifefordota]

Thanks for the information.

I didn't know that the post was 12 years ago.
Time flies.

 

[wuffwaff]

Yes it does....

Aleph 5 is still in action now and then.

William

 

[lifefordota]

Hi,

it will depend a bit on the exact values of your transistors but approximately yes.

I didn't compare one or two transformers sound wise, the advantage of two was packaging and maybe a bit less mechanical noise.

William

also to confirm that the original r 19 is 221k and r 21 is 453 ?

 

[wuffwaff]

No,

they are not. I will have to check the values I used.

William

 

[lifefordota]

Not sure whether would you help put the schematic of yours with value for me to refer.

I'm new in diy

 

[wuffwaff]

Hi,

just checked R19 is 27k, R21 is 510R.

27k to get the bias current down to 2A, 510R to get the ac-current gain to 50%.

All other values are as in the official schematic.

william

 

[lifefordota]

To increase bias , reduce r19
To increase AC source gain , reduce r21 as well?

 

[wuffwaff]

To increase bias, R19 musst be made bigger
To increase AC-current-gain, R21 must be made smaller

 

[lifefordota]

What about pulling off r19?there are people suggesting pulling off to increase bias and maintain r21 as original

I thought increase bias is reduce value of r19?

 

[wuffwaff]

Without R19 the bias will be the highest.

Try to understand the schematic, that helps a lot.

William